Coaxial switch



1. METH ET AL Oct. 16, 1956 COAXIAL SWITCH 2 Sheets-Sheet 1 )NVENTOR. lJEfiEL ME 7H BY FOBEEIJ. WOHL Filed May 21, 1954 United States Patent COAXIAL SWITCH Israel Meth and Robert J. Wohl, New York, N. Y.

Application May 21, 1954, Serial No. 431,621

2 Claims. (Cl. 200156) (Granted under Title 35, U. S. Code (1952), see. 266) The invention described herein may be manufactured and used by or for the Government of the United States of America for governmental purposes without the payment of any royalties thereon or therefor.

This invention relates to a coaxial switch, and more particularly to a shielded, very low capacity, plural coaxial terminal switch.

It is recognized that in the prior art there are numerous examples of single-actuator plural-terminal switches for affording selective circuit combinations among elements external thereto. Prior art switches further include those having single actuators of the rotary type supporting bridging members for afiording selective circuit combinations among several separate circuit subcombinations having terminals connected thereto. However, the prior art does not contain any switch having three or more coaxial terminals and a single rotor actuator for affording a number of circuit arrangements among the three or more terminals of the switch which circuit arrangements include grounding to the switch body any one or more of the terminals, isolating any one or more of the terminals, and electrically connecting two or more of the terminals and wherein the switch structure introduces substantially no capacity between terminals or between any one terminal and the switch body. Furthermore, the prior art discloses no switch having three or more terminals and being so constructed as to introduce substantially no capacity between or among any of its terminals, while affording excellent internal and external shielding with provisions for grounding or isolating any of the switch terminals. Prior art switches introduce radio frequency impedance. No switch of comparable flexibility is known which is so constructed as to completely shield all internal electrical connections therein with substantially no leakage between or among switch elements at different potentials. Furthermore, no switch is known which is adapted to complete two or more separate circuit combinations each of which is completely isolated from the other within the switch, which feature is particularly useful at high frequencies.

This invention marks a departure from the prior art in that it provides a switch comprising a minimum number of parts including a unitary conductive switch body of a material which serves to afford excellent electrostatic shielding and more particularly, excellent radiofrequency shielding, among all the separate circuit completing elements included therein. Terminals of conventional coaxial construction are mounted on the switch body; extending into the switch body from each terminal is an insulated resiliently mounted contact-making assembly. A single rotary switch actuator is mounted in the switch body transverse to the switch terminals. The rotary actuator like the switch body is made of conductive material. If any of the contact assemblies associated with the terminals of the switch engage the rotary actuator directly, those contact assemblies and their respective terminals are grounded through the rotary actuator to the switch body. The rotary actuator is additionally pro- 2,767,286 Patented Oct. 16, 1956 vided with insulating inserts for selectively isolating particular terminals of the switch. Additionally, highly conductive bridging members are insulatably supported within the contour of the rotary actuator for electrically connecting any pair of the switch terminals while introducing substantially no radiofrequency impedance into the circuits so completed. The rotary actuator and the body of the switch are so formed that there is a very closesliding fit between the rotary actuator and the housing for the express purpose of minimizing leakage between unconnected switch terminals. The switch includes a position-indexing detent and suitable position indicator markings etched into the rotary actuator, operating in conjunction with a fiducial line etched into the switch body. The contact and terminal assemblies are respectively identical, reducing cost and simplifying assembly and disassembly.

An object of this invention is to provide a coaxial switch.

A further object is to provide a coaxial switch affording thorough shielding from stray electrostatic and radiofrequency fields.

A further object is to provide a coaxial switch affording excellent shielding from stray electrostatic and radiofrequency fields while introducing substantially no capacitive susceptance between bridged terminals and unused terminals.

A further object is to provide a coaxial switch characterized by excellent shielding, minimum radiofrequency impedance in circuit connections and minimum leakage.

A further object is to provide a shielded coaxial multicircuit switch for selectively affording conditions of circuit continuity, grounding and isolating according to a desired pattern.

A further object is to provide a plural terminal coaxial switch characterized by substantially no capacitive shunts among its terminals, excellent shielding from external electrostatic or radiofrequency fields, provisions for grounding, and plural completely separate electrical connections between combinations of its terminals.

Other objects and many of the attendant advantages of this invention will be readily appreciated as the same becomes better understood by reference to the following detailed description when considered in connection with the accompanying drawings wherein:

Fig. l is a side plan view with parts in section of a ferred embodiment of the invention,

Fig. 2 is a top plan view of the embodiment of the invention shown in Fig. 1,

Figs. 3, 4, and 5, are top, front, and longitudinal sectional views, respectively, of the switch housing,

Figs. 6, 7, and 8, are plan views of the rotary, actuator of the switch taken degrees apart,

Fig. 9 is an end view looking toward the right of Fig. 6,

Figs. 10 and 11 are sectional views taken along the lines 1010 and 1111, respectively, of Fig. 7.

The single embodiment of the invention shown on the drawings is a switch 20 (Fig. l). The switch 20 includes a switch body 22 (Figs. 3, 4, and 5). The housing 22 is premade of conductive material to combine the characteristics of strength, rigidity, and high conductivity suitable to the operating conditions. For example, if the switch is to be used at extremely high frequencies, substantially all parts of the switch necessarily must be plated with silver or gold to reduce skin effect. Likewise, other conditions such as high current level or hard usage requiring frequent switching, in turn, dictate the proper materials well known to those skilled in the art, for use under those conditions. The switch body 22 is elongated and externally formed with oppositely disposed grooves 24 and 26 extending from one end thereof-to its other end.

in the longitudinal dividing plane indicated by the section line 5 of Fig. 3. Extending radially from the axis of the bore 28 and disposed inthe dividing plane of the switch body 22 are the axes of a series of bores 32, 34, and 36. The diameter of each of the bores 32, 34, and

e 36, are stepped down at their inner ends to define coaxial shoulders 33, 35, and 37,'respectively. Each terminal and associated contact assembly of the switch 20 is secured in one of the radial bores. An additional bore is formed in the housing 22 at the lower end thereof (Fig. 5) and includes an internally threaded portion 38, a uniform round portion 42 terminating in a conically shaped reduced portion 44. At assembly,'the bore including the portions 3% 42, and 44, serves to receive a biased detent assembly.

The rotary actuator 52 (Figs. 6-11) of the switch 20 is of conducting material and is in. the form-of a right circular cylinder having a coaxial reduced end portion '54. The rotary actuator 52 is designed for three switch positions and is formed with. three detent-receiving recesses'56, 58, and 62. The three detent-receiving recesses are spaced 120 degree apart about the axis of the rotary actuator 52. In longitudinal alignment with the recess 56, there is formed in the actuator 52 a pair of recesses 64 and 66. A pair of insulating inserts 65 and 67 are secured within the recesses 64 and 66, respectively. The insulating inserts 65 and 67 are suitably shaped at their outer ends to form a continuation of the surfaceof the cylindrical actuator 52. The rotary actuator '52 is formed with additional recesses 68 and 72 for receiving insulating insert 69 and 73, respectiyely, displaced angulariy 120 degrees each way frorn'the inserts 65 and 67. The shaft is recessed to form two 'longitudinaliy extending slots 76 and 78, lZO'degrees apart. In each of the slots 76 and 78 there is secured hollowed-out i insulating shields $2 and S3, respectively. Secured Within the hollowed-out shields 8 2 and 83 are identical elon, gated bridging members 84 and 85, respectively. Each 7 comprises a central thin portion 86, terminating at each continuations of the surface of the rotary actuator 52.

Suitable auxiliary bores are formed diametrically through the rotary actuator 52 for registration with each of the slots 76 and 73. These auxiliary bores permit pushing. out the insulating shoes from the rotary actuator for purposes of replacement. The outer surface of the rotary actuator 52 is formed to be smooth and even to allow a very close sliding fit within the longitudinal bore 28 of the switch body 22. The rotary actuator 52 is retained in the housing 22 by means of a disk 96 press-fitted or soldered into the bottom of the bore 28 of the housing 22.

At its opposite end the rotary actuator 52 is retained in the housing 22 by means of an end member 102 fastened. to the housing 22 by means of screws 104 extend-' ing through the member 102 and into the threaded openings 106 (Fig. 3) of the housing'22. A knurled knob 108 is fastened by means of a set screw to the reduced end 54 of, the rotary actuator 52. Etched into the top surface of the knob 108 are suitable indicia 112. The indicia 112 cooperate with the fiducial mark 114 etched into the member 102. The indicia 112 in cooperation with the fiducial mark 114' is adapted to indicate each of the three positions of the rotary actuator 52. The rotary actua.or 52 is retained in each of its positions by spring biased indexing means located in the bore 42 at the bottom of the housing 22. The indexing means includes. a ball detent116or its equivalent, a compression 4 spring 118, and a screw 122, for permitting the assembly of the ball detent 116 and the compression spring 118 in the bore 42 and in addition to serve as an adjustment means for the bias of the spring 118. The ball detent 116 is. prevented from being forced out of the bore 42, when the rotary actuator 52 is disassembled from the housing 22, because of the reduced conical portion 44 of the detent receiving bore. The ball detent 116 is adapted to seat in the recesses 56, 58, and 62 of the rotary actuapositioning the knob and then tightening the set screw.

As an alternative an indexing recess may be drilled into projection 54 of part 52, into which the set screw may be tightened.

Switch 211 includes three terminal assemblies 132, 134, and 136. The terminal assemblies are identical to one another and are supported by a side cover plate 138. The side cover plate 138 is secured to the switch body 22 by means of screws passing through the side coverplate 138 and .engaging within threaded openings 142 (Fig. 4), formed in the switch body 22. Each of the terminal assemblies include a pair of conventional coaxial terminal members 144 and 146. The outer terminal member 144 engages with the metallic cover plate 138 and is therebygrounded. The inner terminal member 146 is insulatably secured to the cover member 133 through the use of insulating flanged sleeves 152 and 154. The flange of the sleeve 154 serves to insulate the terminal member 146 from the terminal member 144. The outside diameters of the sleeves 152 and 154 are such that they snugly fit within the bores 156 formed in the cover plate 138. A screw 158 and a conductive nut 162, both of conducting material serve to secure the terminal members 144 and 146 relative to the cover plate 138. The resulting assem= bly is characterized by minimum distributive capacitance, high conductivity, and excellent shielding. Associated' with each terminal assembly is a button contact 164.

Each button contact 164 is .insulatably supported within one of the transverse bores of the switch. body 22' by means of a sleeve 166 internally reduced in diam'eterat 168. A compression coil spring 172 of conducting mate'- rial is provided within the insulating sleeve 166' and is compressed between the nut 162 of the terminal assembly and the button contact 164.. The spring 172 insures good contact between the button 164 and the rotary actuator'52.

Except for the terminal members,- the circuit completing elements of the switch 20 are completely shielded by the conductive switch body 22, member 192,v and the cover plate 138. The rotary actuator '52 is grounded to' the 7 switch body 22 with the grounding assured by the closesliding fit between the rotary actuator 52 and the switch body 22, in addition to the bearing relationship between the rotary actuator 52' and the switch body 22 in the plane of the ball' detent 116, as well as the conducting path through the detent itself. The bridging members supported in the rotary actuator 52- are reduced in thickness between their contact-making ends to the limit permitted by operational requirements of strength and cutrent-carrying capacity. The reduction in thickness to a minimum between the contact-making ends serves to reduce the distributed capacity of the bridging member relative to switch body 22. Since the transverse dimension of the bridging member is small and since there is a reasonable space between the bridging element and V the switch body 22, the distributed capacity between the bridging member and the switch body is minimal.

The choice of materials is governed by conditions of use, which conditions vary with the power-handling re-' quirements, the frequency of energy in circuits'controll'ed switch in a particular piece ofequipment; Inside the switch, each of the separate circuit completing assemblies extending transversely through the switch body 22 are completely shielded from one another. For each position of the rotary actuator 52, each button contact is either grounded to switch body 22 through the rotary actuator 52, or is kept isolated by hearing against one of the insulating inserts in the rotary actuator 52, or is connected to another of the terminals through one of the bridging members in the rotary actuator. Because of the close sliding fit of the rotary actuator relative to the switch body, leakage is at a minimum.

Though only three terminal assemblies are shown, this invention may include a larger number of terminals. Furthermore, though only three positions of the rotary actuator are indicated, the switch may be designed so that the rotary actuator can assume a larger number of positions, each of which afford a different combination of circuit arrangements among its terminals. When the switch contains a larger number of terminals, the rotary actuator may be designed to complete more than one electrical connection, whereby there is completed at least two circuits isolated from one another within the switch, The switch may be designed to provide any combination of grounding, isolating and bridging arrangements desired. In the switch, as described, a circuit arrangement provided for by any position of the rotary actuator is completely independent of the circuit arrangement provided by any other position of the rotary actuator. In other words, the bridging members for each position of the rotary actuator are separate and distinct.

In operation, the switch may be plugged into a suitable panel board including a plurality of coaxial terminals adapted to receive the terminals of the switch 20. By means of the knob 108 which is thoroughly grounded through the switch body, and the outer terminal member of the panel board, or the like into which it is plugged, the actuator may be rotated to afford the circuit arrangement desired.

This invention may be utilized in combination with the adaptor disclosed and claimed in copending application Serial No. 429,411 filed May 12, 1954, by David H. Andrews et al., for Adaptor for Capacitance Meters and further identified as Navy Case No. 14,390. The structure of the switch described is characterized by minimum distributed capacity, excellent shielding, provision for grounding, isolating, and bridging, and in addition affords a multiplicity of connections for its plurality of terminals. This is all accomplished with simplicity of construction and ease of operation.

Obviously many modifications and variations of the present invention are possible in the light of the above teachings. It is therefore to be understood that within the scope of the appended claims the invention may be practiced otherwise than as specifically described.

We claim:

1. A coaxial switch comprising an elongated switch body of conductive material, a plurality of combination contact and terminal assemblies mounted transversely in said switch body and extending from said switch body, said assemblies each defining an axis, the axes of said assemblies being parallel and coplanar, said switch body being formed with a smooth and even bore defining an axis coplanar with and perpendicular to the axes of said assemblies, each of said assemblies including contact making portions biased to extend into the longitudinal bore of said switch body, an elongated cylindrical rotor of conducting material retained in the longitudinal bore of said body and being so constructed that at assembly there is a close sliding fit between said rotor and said switch body throughout the length of said actuator included in the bore of said switch body whereby there is maximum external and internal shielding and minimum leakage between any of said assemblies; indexing means in part formed in said rotor and in part mounted in said switch body for defining each of a plurality of rotary positions of said rotor relative to said switch body, a plurality of separate narrow insulated bridging elements recessed longitudinally into said rotor at as many respective angular indexing positions around said rotor and at as many respective longitudinal positions along said rotor whereby a different adjacent pair of said assemblies is electrically connected at each indexed position of said rotor.

2. A coaxial switch comprising an elongated conductive body formed with a longitudinal circular bore and with three parallel openings whose axes define a plane including the axis of the bore; a solid circular conductive rotor of substantially the same diameter as the bore disposed in the bore for a close sliding fit within said body; indexing means engaging said body and rotor for defining three angular positions of said rotor in said body; insulating means in each of the three openings formed in said body; three spring-biased contacts slidably disposed in respective ones of said insulating means for movement into the bore; first and second insulating inserts recessed flush into said rotor at positions where they are in alignment with and engaged by the end ones of said contacts in a first of the indexed positions of said rotor; a third insulating insert recessed flush into said rotor for alignment with and engagement by an end one of said contacts in a second of the indexed positions of said rotor; a fourth insulating insert recessed flush into said rotor for alignment with an engagement by the other end one of said contacts in a third of the indexed positions of said rotor; first and second elongated insulating inserts recessed fiush into said rotor in longitudinal alignment with said third and fourth insulating inserts respectively, said elongated insulating inserts being constructed and arranged to extend from the center one of said contacts to respective end ones of said contacts; a bridging member recessed into each of said elongated insulating inserts and being flush at each end thereof with the surface of said rotor and being recessed between the ends.

References Cited in the file of this patent UNITED STATES PATENTS 2,556,869 Charles June 12, 1951 2,565,643 Baddour Aug. 28, 1951 2,599,314 Bobb June 3, 1952 

